Pump with pressure relief



June 25, 1968 5 HERRSTRUM ET AL 3,389,660

PUMP WITH PRESSURE RELIEF 2 Sheets-Sheet 1 Filed Aug. 15, 1966 June 25, 1968 HERRSTRUM ET AL 3,389,660

PUMP WITH PRESSURE RELIEF Filed Aug. 15, 1966 2 Sheets-Sheet 2 lab? United States Patent O 3,389,660 PUMP WITH PRESSURE RELIEF Rudolph E. Herrstrum, Rockford, and Richard F. Van Allen, Loves Park, 11]., assignors to Greeulee Bros. & Co., a corporation of Illinois Filed Aug. 15, 1966, Ser. No. 572,533 4 Claims. (Cl. 103-5) ABSTRACT OF THE DISCLOSURE A hydraulic power system including a main pump having opposed cylinders and a secondary rotary pump in the same housing for supplying fluid to the main pump, in which a piston and cylinder operated relief valve is provided adjacent the inlets of both cylinders, the relief valves being positioned opposite from each other and adjacent the rotary pump outlet so that the relief valves open the cylinders when flow from the rotary pump ceases.

This invention relates to hydraulic pumps and more particularly to a pump having a high pressure piston type pump means and means to relieve the pressure on the pistons when the pump motor is stopped so as to facilitate restarting of the pump by reducing the star-ting torque required.

It is the general object of the invention to provide a piston type pump with new and improved pressure relief means operable when the pump is stopped.

Another object is to provide a pump having a high pressure piston and cylinder stage with a relief passage from the pump cylinder to a low pressure reservoir, a low pressure pump means pumping fluid from the reservoir to the cylinder of the high pressure stage, a relief valve for controlling said relief passage, and a piston for operating said relief valve in a direction to close it when the pump is operating and permitting the high pressure to open it when the pump is stopped.

Other objects and advantages will become readily apparent from the following description, taken in connection with the accompanying drawings in which:

FIG. 1 is a vertical view partly in central section of a preferred form of the invention;

FIG. 2 is a vertical section approximately along the line 22 of FIG. 1;

FIG. 3 is a horizontal section approximately along the line 33 of FIG. 1; and

FIG. 4 is a horizontal section approximately along the line 44 of FIG. 1.

As shown in the drawings, a preferred form of the invention is embodied in a pump indicated generally at located in a reservoir casing 21 and suspended from.

a reservoir cover member 22 by -a plurality of bolts 23-. An electric motor 24 is supported on the upper end of the reservoir cover by means of bolts 25 and has a shaft 26 extending downwardly therefrom and into and keyed to a tubular coupling member 27 which is carried on the upper end of a pump shaft 28.

The pump comprises generally a rectangular cylinder block 29, the upper surface 30 of which is positioned against the reservoir cover and is secured thereby by the bolts 23, and a lower end plate 31 which may be secured to the block 29 by bolts 32.

The cylinder block 29 has a central bore 33 therein through which the pump shaft 28 extends and is supported in an upper ball bearing 34 and a lower ball bearing 35. The shaft has an eccentric portion 36 formed thereon which carries a roller bearing 37.

The pump has a high pressure stage herein shown as comprising a pair of pistons 38 and 39 located in opposed relation and slidably supported in tubular cylinder liners ice 40 and 41, respectively, located in horizontal bores 42 and 43 in the cylinder block. The inner ends of the pistons engage the roller bearing 37. The outer ends of the pistons reciprocate in pumping chambers 44 and 45 formed in the liners 40 and 41, respectively, and by the plugs 46 and 47 which abut the ends of the liners.

The pump, in the form shown, also has a low pressure pump means. Thus, the lower end 28 of the pump shaft is arranged to drive a vane type pump, generally designated 48, supported on the pump plate 31 and provided with an inlet nipple 49 which normally extends below the fluid level in the reservoir. A strainer 50 is located between the nipple 49 and an inlet port 51 (FIG. 4) for the low pressure pump means formed in a bottom plate 52. An outlet port 53 (FIG. 4) in an upper plate 54 communicates with passageways forming inlets to the pump chambers 44 and 45 and which comprise passages 55 in the pump plate 31 and connecting passages 56, 57 and 58 in the cylinder block 29. The passage 58 communicate with annular passages 60, formed by reduced portions of the cylinder liners 40 and 41, the ports 61 extending through the walls of the cylinder liners.

The inlet passageways to the pump chambers 44 and 45 are controlled by ball type check valves 62 which are backed by springs 63, plugs formed by balls 64 and threaded members 65.

Outlet passages extend from the pumping chambers 44 and 45 through the cylinder block and are herein shown as comprising vertically extending ports 66 having valve seats 67 formed therein, horizontally extending ports 68 somewhat parallel to the pistons 38 and 39 and transverse ports 69 (FIGS. 1-3) extending at right angles to the ports 68. A passage 70 connects the two ports 69. Outlet passage check valves 71 are normally spring pressed against the seats 67; 72 is an outlet passage.

Normally in the operation of a motor driven pump of the type herein disclosed, the pump is started and stopped by starting and stopping the electric motor. With the check valve system shown, upon stoppage of the pump the pressure in the pumping chambers 44 and 45 remains at its normal high value as, for example, 10,000 p.s.i. Such pressure in the pump chambers produces an abnormal starting load on the motor.

The invention provides means for relieving the pressure in the pump chambers when the pump is stopped. AS shown herein this means comprises relief passages consisting of ports and 81 communicating with the passages 57 between the check valves 62 and the pump chambers 44 and 45. The relief ports 80 and 81 are normally closed when the pump is operating by relief valves 82 and 83, respectively, which are carried on pistons 84- supported in the pump plate 31 in cylinders 85. The lower portions of the cylinders are connected to receive fluid from the low pressure vane type pump 48 by means of passages 86 and 87 which extend between the cylinders and the passages 55.

When the pump is operating the low pressure fluid from the vane type pump 48 serves to keep the pistons 84 in their upper valve closing positions as shown. When, however, the pump is stopped the discharge pressure of the vane pump drops and permits the pistons 84 to descend under the action of the high pressure fluid against the tops of the valves 82 and 83. Fluid from the high pressure pump chambers 44 and 45 is then relieved through the passages 80 and 81, the upper portions of the cylinders and passages 90 and '91 in the pump plate 31 which discharge into the reservoir.

Removal of the high pressure in the pumping chambers 44 and 45 permits the pump to be restarted with a minimum starting torque requirement on the motor 24.

We claim:

1. A pump having, in combination, a housing, a pair 3 of opposed high pressure piston and cylinder devices in said housing, a shaft rotatably mounted in said housing and carrying means to eifect pumping by said devices, an outlet valve controlling the outlet of fluid from each of the cylinders, a low pressure rotary pump in said housing driven from said shaft and adjacent said piston and cylinder devices, means for controlling the supply of fluid from the low pressure pump to the cylinders including passage means in said housing between the rotary pump and each of said cylinders, inlet valves in each of said passage means, a reservoir for supplying fluid to the low pressure pump, and means forming pressure relief passages in said housing from each of the inlet passages between the inlet valves and the high pressure cylinders, said relief passages communicating with the reservoir, generally opposed pressure relief valves in said housing for controlling the flow of fluid through said pressure relief passages, piston and cylinder devices for operating said pressure relief valves, and passage means in said housing for supplying fluid from the low pressure rotary pump to each of said valve operating pistons to close the pressure relief valves when the low pressure pump is operating.

2. A pump as defined in claim 1 wherein the inlet and outlet valves for the high pressure piston and cylinder devices are check valves. i

3. A pump as defined in claim 2 wherein the low pressure rotary pump is of the vane type.

4. A pump as defined in claim 2 wherein the pressure relief valves have surfaces subjected to high pressure fluid from the cylinders of the high pressure piston and cylinder devices which are operable when the lowpressure rotary pump stops to overcome the opposing pressure on the relief valves operating pistons to open the relief valves.

References Cited UNITED STATES PATENTS 1,909,972 5/1933 Le Valley 230-26 X 1,968,985 8/1934 Black 230-30 X 2,115,546 4/1938 Aikman 23030 X 2,668,004 2/1954- .Browne 23026 2,883,934 4/1959 Roosa 103-5 X 3,146,715 9/1964 Knudson 103-41 X 3,150,593 9/1964- Funk et al. 1035 3,309,995 3/1967 Tyler 10341 X FRED C. MATTERN, JR., Primary Examiner.

WARREN I. KRAUSS, Assistant Examiner. 

